TITRATION OF THE COMPLEMENT. 



137 



control tube, and form there a large deposit, a trace of hemolysis or almost 

 o would be the terms used in reporting the results. Tube 7 after two hours 

 showed incomplete hemolysis, i.e., compared with control III it was noticeably 

 clearer, but not completely transparent. After twenty-four hours there was 

 a small mass of undissolved red blood cells at the bottom of the test tube and 

 above it a deep red fluid which was only slightly different from that in the 

 tubes where the erythrocytes were completely dissolved. If this sediment 

 should become so small that on shaking only a cloudy turbidity is produced, 

 the result would correspond to the designations "very small sediment," 

 " occasional erythrocytes at the bottom of the tube," or " almost complete 

 hemolysis." 



In the tubes containing inactive hemolysin without complement (control i, and in 

 complement binding reactions) hemagglutination can occur because the agglutinins 

 which also exist in the serum become active. Hemagglutination is recognized by the 

 fact that on shaking the sediment, the erythrocytes are not equally distributed, but remain 

 in clumps or strings and soon sink to the bottom again. 



For many purposes it is desirable to titrate the complement 



Titrationofthe content of a serum. The method is the same as that used 



Complement, in hemolysin titration, only with the difference that a fixed 



amount of hemolysin and varying quantities of complement 

 are employed. 



The titer of this complement when employed with a hemolysin of i/iooo strength 

 and allowed to stay in the incubator for two hours would be 0.04. 



The complement content of the serum of a healthy guinea-pig is fairly 

 constant. During illness the titer usually is decreased. Among healthy 

 people the complement titer shows marked individual variations. 



For hemolysis a definite quantitative relationship between hemolysin 

 and complement is necessary. 



<* On the basis of the two titrations outlined above, it has been estimated 

 that at least 0.04 c.c. complement is necessary to activate o.ooi c.c. of 

 hemolysin. If less complement is used with the same amount of hemolysin, 

 hemolysis does not occur or else it is incomplete. If the quantity of hemo- 



